In the market, there is a wide variety of drive wrenches for nuts; for example, U.S. Pat. No. 7,082,858, which describes a hydraulic torque wrench having a separate ratchet unit and hydraulic cylinder drive unit connectable by an overlapping cylindrical connection at selected angles of rotation providing clearance in use. The hydraulic cylinder actuates the ratchet mechanism by a connecting rod traveling through the overlapping cylindrical connection and engaging a pivotable drive plate.
The ratchet unit case may be integral, or split for removable accesses to the ratchet mechanisms. The cylinder unit hydraulic connections may be separate rotatable connections or a single connection and collar, allowing three-way rotation, but having the disadvantage of not being autonomous and of depending on several connections in order to operate.
Another example is the invention described in document US 2002/0121161 A, which refers to a fluid-operated tool having a ratchet link assembly provided with ratcheting mechanism for engaging and turning a threaded connector, a fluid-operated drive assembly releasably connectable with the ratchet link assembly, and a unit for releasably connecting the fluid operated drive assembly with the ratchet link assembly, the connecting unit including an opening provided in one of the assembly, a projection provided in the other of the assemblies and insertable into the opening, and a blocking member which block the projection in the opening in an assembled condition of the assemblies, the blocking member being operable by a user to unblock the projection and to allow withdrawal of the projection from the opening so as to release the assemblies from one another. The invention of the cited document is not an autonomous tool and has not a practical use.
The invention described in document U.S. Pat. No. 6,260,444 B1, refers to a power tool for tightening and loosening threaded connectors has a housing, comprising a ratchet unit for turning an engaging element so as to turn a threaded connector engaged by the engaging element, a first hydraulic drive unit including a drive housing and a hydraulically movable driving element, a non-hydraulic drive unit including a drive housing and non-hydraulically moveable driving element, a first connection provided on the link housing and on the drive housing of the hydraulic drive unit and the non-hydraulic drive unit, so that alternatingly either the housing of the hydraulic drive unit or the housing of the non-hydraulic drive unit can be connected with the link housing, and a second connection for connecting the ratchet mechanism alternatingly with the driving element of the hydraulic drive unit or the driving element of the non-hydraulic drive unit, so that the driving element of the hydraulic drive unit and alternatingly the driving element of the non-hydraulic drive unit during its movement turns the ratchet mechanism of the link and thereby turns a threaded connector engaged by the engagement element of the link to be tightened or loosened.